Substrate processing method and substrate processing apparatus

ABSTRACT

The wafers W are dipped and rinsed in pure water in the processing bath  60,  and then dichloromethane is fed into the processing bath  60,  thereby changing the state of the wafer W from being dipped in pure water to being dipped in dichloromethane. Thereafter, the wafers W is raised up to the drying chamber  61,  and dichloromethane remained on the surface of each wafer W is evaporated, and the hot N 2  gas is discharged onto the wafers W. Thereby, no water marks are produced, and no resist is dissolved, and the substrate can be dried in safety.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a substrate processing methodand a substrate processing apparatus for processing a substrate.

[0003] 2. Description of the Related Art

[0004] In the manufacturing process of a semiconductor device, varioustypes of cleaning systems are employed in order to clean a semiconductorwafer (hereinafter referred to as “wafer”) using a cleaning liquid suchas a chemical liquid and pure water, thereby removing contamination suchas particles, organic contaminants, and metallic impurities, whichadhere to the surface of the wafer. As one of the above cleaningsystems, a wet-type cleaning system, which cleans wafers by submergingthem in a cleaning liquid stored in a cleaning bath, is widespread.

[0005] Such a cleaning system performs: a cleaning process using achemical solution mainly composed of ammonium, hydrochloric acid andfluoride acid and also using pure water; a final rinsing process usingpure water; and a drying process. The cleaning system has a final rinsecleaning unit that performs the final rinsing process and a drying unitthat performs the drying process.

[0006] These drying units execute, for example, an IPA vapor dryingmethod. In the IPA vapor drying method, vapor of IPA [isopropyl alcohol:(CH₃)₂CHOH ], which has a high hydrophilic property, is fed onto a wafercontained in a drying chamber. Waterdrops remaining on the wafer surfaceare removed with volatilization of IPA, and thus the wafer is dried.

[0007] When conveying the wafer from the final rinse cleaning unit tothe drying unit, the wafer surface is exposed to the air, and thuswaterdrops remaining on the wafer surface are likely to be dried,producing water marks. Furthermore, the final rinse cleaning unit andthe drying unit are arranged side by side, thus a large footprint isrequired.

[0008] With the goal of avoiding generation of water marks and reducingfootprint, a rinsing/drying unit that performs both the final rinsingprocess and the drying process has been introduced. The rinsing/dryingunit is configured so that, after completion of the final rinsingprocess, IPA vapor is fed when pulling up a wafer submerged in purewater stored in a cleaning bath, thereby drying the wafer by Mangoranieffect stemming from the difference in surface tension between water andIPA.

[0009] However, the conventional drying device and the rinsing/dryingdevice employ IPA, which has a property of dissolving a resist. When IPAvapor or IPA liquid is fed onto a wafer surface provided with a resistfilm formed according to a predetermined circuit pattern, the surface ofthe resist film is dissolved and the pattern might be broken.Furthermore, with the memory circuit, in the event that a dual gate forsuppressing a leakage current is formed on the wafer and has a structureof locally depositing the resist film for patterning, if IPA vapor isfed to it, the dual gate is changed in thickness, and the operation ofthe circuit thus may be adversely affected. Furthermore, since IPAcontains an alcoholic component, there is a risk of fire. As a result,sufficient safety measures and facilities are required.

[0010] Furthermore, in order to achieve the Mangorani effectsufficiently, the wafer must be raised from pure water slowly, and aconsiderable amount of time is thus required to move the wafer upward.In addition, a wafer guide is provided with a plurality of grooves tohold the periphery of each wafer. Water also remains in the grooves andnarrow regions between the wafer periphery engaged in the grooves and onthe groove surfaces. Unlike the exposed wafer surface, IPA vapor hardlyreaches into these narrow regions, and thus they are hardly dried.

SUMMARY OF THE INVENTION

[0011] Therefore, an object of the present invention is to provide asubstrate processing method and apparatus that can process a substratesafely, without producing water marks and without breaking a pattern ofa resist film formed on the substrate.

[0012] To accomplish the above objective, the present invention providesa substrate processing method including the steps of: placing asubstrate in a first processing liquid stored in a processing bath;feeding a second processing liquid different in specific gravity fromthe first processing liquid into the processing bath, thereby forming afirst layer of the first processing liquid and a second layer of thesecond processing liquid with an interface being formed therebetween;and causing a relative movement of the interface and the substrate sothat the substrate passes through the interface and the substratelocates on a second layer side of interface.

[0013] The relative movement of the interface and the substrate may beproduced by draining the first liquid from the processing bath whilefeeding the second processing liquid into the processing bath.

[0014] When the specific gravity of the second processing liquid issmaller than the specific gravity of the first processing liquid, therelative movement of the interface and substrate may also be produced bymoving the substrate upward.

[0015] The aforementioned method may further include a step ofpositioning the substrate outside the second layer and drying thesubstrate, after the substrate has passed through the interface by therelative movement of the interface and the substrate.

[0016] Preferably, the method according to the present invention can beused for processing a substrate having a resist film formed on thesurface of the substrate. In such a case, preferably, the secondprocessing liquid has a property of not-dissolving the resist film. Thesecond processing liquid is preferably incombustible.

[0017] When the second processing liquid is fed, a third processingliquid may be fed, the third processing liquid being substantiallyinsoluble in the first and the second processing liquids and having aspecific gravity between those of the first and the second processingliquids is fed, thereby a third layer of the third processing liquid isformed along the interface between the first layer and the second layer,whereby the interface enters into a first layer side in the neighborhoodof the point where the interface contacts the substrate.

[0018] Alternatively, the second processing liquid may be fed in aheated state into the processing bath, thereby the second layer entersinto a first layer side in the neighborhood of the point where theinterface contacts the substrate.

[0019] The present invention also provides a substrate processingapparatus for processing a substrate in a processing bath, whichincludes: a substrate holder that holds the substrate in the processingbath, a first processing liquid feed nozzle that feeds the firstprocessing liquid into the processing bath, and a second processingliquid feed nozzle that feeds a second processing liquid different inspecific gravity from the first processing liquid into the processingbath.

[0020] The substrate processing apparatus is preferably structured sothat it further includes a first processing liquid draining means fordraining the first processing liquid from the processing bath and asecond processing liquid draining means for draining the secondprocessing liquid from the processing bath.

[0021] The substrate holder is preferably movable up and down betweeninside the processing bath and above the processing bath.

[0022] Furthermore, the substrate processing apparatus is preferablystructured so that it further includes a gas feeding means for feeding agas that promotes drying the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a perspective view of a cleaning system equipped with anrinsing/drying unit, which is the first embodiment of the presentinvention;

[0024]FIG. 2 is a piping flow diagram of the rinsing/drying unit shownin FIG. 1;

[0025]FIG. 3 is a perspective view of the wafer guide shown in FIG. 2;

[0026]FIG. 4 is a flow chart showing the processing procedure executedin the rinsing/drying unit shown in FIG. 2;

[0027]FIG. 5 is an illustration explaining the first step of the processperformed by the rinsing/drying unit shown in FIG. 2;

[0028]FIG. 6 is an illustration explaining the second step of theprocess performed by the rinsing/drying unit shown in FIG. 2;

[0029]FIG. 7 is an illustration explaining the third step of the processperformed by the rinsing/drying unit shown in FIG. 2;

[0030]FIG. 8 is an illustration explaining the fourth step of theprocess performed by the rinsing/drying unit shown in FIG. 2;

[0031]FIG. 9 is an illustration explaining the fifth step of the processperformed by the rinsing/drying unit shown in FIG. 2;

[0032]FIG. 10 is an illustration explaining the sixth step of theprocess performed by the rinsing/drying unit shown in FIG. 2;

[0033]FIG. 11 is a piping flow diagram of a rinsing/drying unit, whichis the second embodiment of the present invention;

[0034]FIG. 12 is a flow chart showing the processing procedure executedin the rinsing/drying unit shown in FIG. 11;

[0035]FIG. 13 is an illustration explaining the first step of theprocess performed by the rinsing/drying unit shown in FIG. 11;

[0036]FIG. 14 is an illustration explaining the second step of theprocess performed by the rinsing/drying unit shown in FIG. 11;

[0037]FIG. 15 is an illustration explaining the fourth step of theprocess performed by the rinsing/drying unit shown in FIG. 11;

[0038]FIG. 16 is a piping flow diagram of rinsing/drying unit, which isthe third embodiment of the present invention;

[0039]FIG. 17 is an illustration explaining the first step of theprocess performed by the rinsing/drying unit shown in FIG. 16;

[0040]FIG. 18 is an illustration explaining the second step of theprocess performed by the rinsing/drying unit shown in FIG. 16;

[0041]FIG. 19 is an illustration explaining the third step of theprocess performed by the rinsing/drying unit shown in FIG. 16;

[0042]FIG. 20 is an illustration explaining the fourth step of theprocess performed by the rinsing/drying unit shown in FIG. 16;

[0043]FIG. 21 is an illustration explaining an alternative of the thirdstep of the process performed by the rinsing/drying unit shown in FIG.16;

[0044]FIG. 22 is a piping flow diagram of a rinsing/drying device, whichis the fourth embodiment of the present invention;

[0045]FIG. 23 is an illustration explaining a modification of the methodof the present invention;

[0046]FIG. 24 is an illustration explaining a modification of the methodof the present invention;

[0047]FIG. 25 is a piping flow diagram of a rinsing/drying unit thatexecutes the method shown in FIG. 24; and

[0048]FIG. 26 is another piping flow diagram of a rinsing/drying unitthat executes the method shown in FIG. 24.

DESRIPTION OF THE PREFERRED EMBODIMENTS

[0049] The preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. FIG. 1 is aperspective view of a cleaning system 1, which includes a rinsing/dryingunit 21 of the first embodiment of the present invention. The cleaningsystem 1 executes a process including the steps of: receiving the wafersW (substrate) contained in carriers C, carrier by carrier; cleaning thewafers W; drying the wafers W; and delivering the wafers W, carrier bycarrier.

[0050] In the cleaning system 1, a receiving/sending-out section 2executes process steps from a step of receiving a wafer carrier Cstoring 25 wafers W (before cleaning) to a step of sending the wafers Wto cleaning place. In the receiving/sending-out section 2, the carriersC placed on a transfer stage 5 is conveyed to a loader 7 by a transferdevice 6 two by two, and then the loader 7 takes out the wafers W fromthe carriers C.

[0051] A cleaning/drying section 10 is provided with: a wafer chuckcleaning/drying unit 11 that cleans and dries a wafer chuck 36 of atransfer device 30 for transferring the wafers W; wafer cleaning units12 to 15 that clean the wafers W using cleaning liquids such as variouschemical liquids and pure water; a wafer chuck cleaning/drying unit 16that cleans and dries a wafer chuck 37 of a transfer device 32; wafercleaning units 17 to 19; a wafer chuck cleaning/drying unit 20 thatcleans and dries wafer chucks 33 a, 33 a of a transfer device 33; and arinsing/drying unit 21 that performs a final rinse cleaning process(rinsing treatment) and drying process for the wafers W cleaned by thewafer cleaning units 12 to 15 and 17 to 19. The above units are arrangedin the above order relative to the receiving/sending-out section 2. Thetransfer devices 30, 31, 32, and 33 are arranged on the front of thecleaning/drying unit 10 (the front side of FIG. 1).

[0052] The wafer cleaning units 12, 14, 17, and 19 are structured so asto perform chemical liquid cleaning (chemical liquid treatment), and thewafer cleaning units 13, 15, and 18 are structured so as to executerinsing, so that chemical liquid cleaning and rinsing are alternatelyexecuted according to the general cleaning process.

[0053] In one embodiment, the wafer cleaning unit 12 executes SPMcleaning using SPM (a mixed solution of H₂SO₄ and H₂O₂), which is acleaning liquid mainly containing a sulfuric acid, and thus removesimpurities such as organic contaminants deposited on the surface of eachwafer W. The wafer cleaning unit 14 executes SC1 cleaning using APM (amixed solution of NH₄OH, H₂O₂, and H₂O), which is a cleaning liquidmainly containing an ammonium, and thus removes impurities such asorganic contaminants and particles adhering to the surface of each waferW. The wafer cleaning unit 17 executes SC2 cleaning using HPM (a mixedsolution of HCl, H₂O₂and H₂O), which is a cleaning liquid mainlycontaining a hydrochloric acid, and thus removes metallic ions adheringto the surface of each wafer W. The wafer cleaning unit 19 executes DHFcleaning using DHF (a mixed solution of HF and H₂O), which is a cleaningliquid mainly containing a fluoride acid, and thus removes an oxide filmformed on the surface of each wafer W. The wafer cleaning units 13, 15,and 18 rinse the wafers W using pure water.

[0054] The arrangement and combinations of the wafer cleaning units 12to 15 and 17 to 19 can optionally be changed depending on the kind ofcleaning process for the wafers W. For example, one of the cleaningunits may be omitted, or a cleaning unit, which cleans the wafers W withanother kind of chemical liquid, may be added.

[0055] In a loading/delivery section 50, twenty-five wafers W cleanedand dried by the cleaning/drying unit 10 are stored in the carrier C,and then the wafers W are delivered carrier by carrier. In theloading/delivery section 50, an unloader 51 puts the cleaned wafers Winto a carrier C, and the carrier C storing the cleaned wafers W istransferred to a delivery unit 52 by means of a transfer device, notshown.

[0056] Next, the structure of the rinsing/drying unit 21, as the firstembodiment of the present invention, will be described. As shown in FIG.2, the rinsing/drying unit 21 has a processing bath 60 for rinsing thewafers W, a drying chamber 61 for drying the wafers W arranged above theprocessing bath 60, and a wafer guide 62 as a means for holding thewafers W.

[0057] The processing bath 60 composed of a box-shaped inner bath 63,which is large enough to store the wafers W, and an outer bath 64. Apure water feed circuit 65 as a first processing liquid feed means forfeeding pure water (DIW) as a first processing liquid is connected tothe processing bath 60. The inlet of the pure water feed circuit 65 isconnected to a pure water feed source, not shown. An open-close valve 66and a flow rate controller 67 are provided in the pure water feedcircuit 65. An outlet of the pure water feed circuit 65 is connected tojet nozzles 68, 68, which are arranged in pairs at the bottom portion ofthe inner bath 63.

[0058] Connected to the pure water feed circuit 65 is a solvent feedcircuit 70 as a second processing liquid feed means for feeding asolvent as a second processing liquid. An inlet of the solvent feedcircuit 70 is connected to a solvent feed source, not shown. Anopen-close valve 71 and a flow rate controller 72 are provided in thesolvent feed circuit 70.

[0059] Dichloromethane or HMDS (hexamethyldisiloxane), which isdifferent in specific gravity from pure water and has hydrophobicproperty, is used for the solvent. Although dichloromethane and HMDS arevolatile, they contain no flammable component such as alcohol, thus evenif vaporized, they are safe. In addition, these solvents do not dissolvea resist film. Thus, in the event that a resist film is formed on thewafer surface according to a predetermined circuit pattern, even if sucha wafer W is submerged in dichloromethane or HMDS, the surface of theresist film is not dissolved, thus preventing breakage of the circuitpattern.

[0060] A pure water drain pipe 81, as a first processing liquid drainingmeans, is connected to the bottom of the inner bath 63 via an open-closevalve 80. A solvent drain pipe 83, as a second processing liquidejection means, is also connected to the inner bath 63 via an open-closevalve 82.

[0061] Connected to the bottom of the outer bath 64 is a pure waterdrain pipe 84, to which a solvent drain pipe 86 is connected via athree-way valve 85. Pure water stored in the inner bath 63 can bedischarged through the pure water drain pipe 81, and switching thethree-way valve 85 to the pure water drain pipe side allows pure waterstored in the outer bath 64 to be discharged through the pure waterdrain pipe 84. The solvent in the inner bath 63 can be dischargedthrough the solvent drain pipe 83, and switching the three-way valve 85to the solvent drain pipe side allows solvent stored in the outer bath64 to be discharged through the solvent drain pipe 83.

[0062] An N₂ gas feed circuit 90, as a gas feed means for feeding N₂(nitrogen) gas at normal temperature or hot N₂ gas, is connected to thedrying chamber 61.

[0063] Connected to the inlet of the N₂ gas feed circuit 90 is an N₂ gasfeed source (not shown) for feeding N₂ gas at normal temperature. Anopen-close valve 91, a flow rate controller 92, and a heater 93 forheating N₂ gas are provided, in that order, in the N₂ gas feed circuit90. The outlet of the N₂ gas feed circuit 90 is connected to gas nozzles94, 94 arranged in pairs at the top portion of the drying chamber 61. Abypass circuit 95 is connected to the N₂ gas feed circuit 90 so that N₂gas at normal temperature can be fed to the drying chamber 61 uponbypassing the heater 93. An open-close valve 96 and a flow ratecontroller 97 are sequentially provided in the bypass circuit 95.

[0064] An exhaust pipe 98 for discharging the atmosphere in the chamberis connected to the side wall of the drying chamber 61. A flow rateregulating valve 99 is provided at the exhaust pipe 98 in order toadjust exhaust rate through the exhaust pipe 98. A cover 100 is providedfor opening or closing a transfer port 61 a formed on a top of thedrying chamber 61. The cover 100 is capable of vertical and horizontalmovement by means of a moving mechanism, not shown.

[0065] The rinsing/drying unit 21 has the wafer guide 62 shown in FIG.3. The wafer guide 62 is capable of vertical movement (movement in the Zdirection as illustrated) by means of an elevating mechanism, not shown.The wafer guide 62 has a shaft portion 105, a guide portion 106, andthree parallel holding members 107 a, 107 b and 107 c horizontally fixedto the guide portion 106. On each of the holding members 107 a to 107 c,fifty slots 108 for holding the lower part of the periphery of eachwafer W are formed at even intervals. The wafer guide 62 is capable ofholding 50 wafers W arranged at even intervals and moving them up anddown between the processing bath 60 and the drying chamber 61.

[0066] Next, the process according to the method of the presentinvention performed by the rinsing/drying unit 21 having theaforementioned structure will be explained together with the cleaningprocess performed by the cleaning system 1.

[0067] Firstly, a transfer robot, not shown, places the carriers C, eachstoring not-cleaned wafers W (for example, twenty-five wafers), on thetransfer stage 5 of the receiving/sending-out section 2. Then, in thereceiving/sending-out section 2, fifty wafers W stored in the twocarriers C are taken out therefrom, and the transfer device 30 holds allfifty wafers at once. The wafers Ware transferred to transfer devices31, 32 and 33, in that order, and the wafers W are thus transferred tothe wafer cleaning units 12-15 and 17-19, in that order. In this way,impurities such as particles adhering to the wafer surfaces are removedand cleaned. Finally, the wafers W are subjected to the final rinsingand drying process in the rinsing/drying unit 21, and they are thenmoved outside the cleaning system 1 from the loading/delivery section 50carrier by carrier.

[0068] Next, the process executed by the rinsing/drying unit 21 will bedescribed referring to the flow chart of FIG. 4 and FIGS. 6-10illustrating process steps 1 thru 6. Here, dichloromethane (liquidphase) is used as the solvent. Dichloromethane has a greater specificgravity than that of pure water, and is hydrophobic, thus almost nevermixes with pure water.

[0069] Firstly, the cover 100 moves to open the transfer port 61 a, andthe wafer guide 62 moves toward the drying chamber 61. The transferdevice 33 conveys the wafers W, having been subjected to DHF cleaning bythe wafer cleaning unit 19, into the rinsing/drying unit 21, andtransfers them to the wafer guide 62. The open-close valve 66 (shown inFIG. 2) is opened, and pure water from the pure water feed circuit 65 isfed into and fills the processing bath 60 via the jet nozzle 68 (seeFIG. 5).

[0070] Next, the cover 100 is closed and the wafer guide 62 moves downto position the wafers W in the processing bath 60. The wafers W arethus dipped in the pure water and are subjected to final rinsing, asshown in FIG. 6 (S1 of FIG. 4).

[0071] After final rinsing, the open-close valve 66 is closed and theopen-close valve 71 is opened, and thus dichloromethane is fed into theinner bath 63 through the solvent feed circuit 70, as shown in FIG. 7(S2 of FIG. 4).

[0072] As mentioned above, since dichloromethane is greater in specificgravity than pure water, dichloromethane moves down and accumulates atthe bottom portion of the processing bath 60. At the same time, purewater is gradually discharged from the upper part of the processing bath60 relative to the injection of dichloromethane, whereby a pure waterlayer and a dichloromethane layer are formed in the inner bath 63.Dichloromethane accumulates and the dichloromethane layer is increasedin thickness, while pure water is discharged from the inner bath 63 andthe pure water layer is reduced in thickness. As shown in FIG. 8,finally, the pure water that fills the inner bath 63 is entirelyreplaced with dichloromethane. As mentioned above, the state of wafers Wis changed from a state of being submerged in pure water to a state ofbeing submerged in dichloromethane (S3 of FIG. 4). According to theabove, the pure water in contact with the wafer surface can be replacedwith dichloromethane, with the wafers W being kept submerged in theliquids (i.e., pure water and dichloromethane) and without the wafers Wcoming into contact with the outer atmosphere (air). In addition, purewater existing on the surface of the wafer guide 62, in the slots 108,and in the narrow regions between the periphery of each wafer W engagedwith the slots 108 and the surfaces of the slots, can also be easilyreplaced with dichloromethane. Then, the N₂ gas feed circuit 90 feeds N₂gas at normal temperature or hot N₂ (nitrogen) gas, so that an inactivegas atmosphere is established in the drying chamber 61. The N₂ gas maybe exhausted via the exhaust pipe 98 so that the atmosphere in thedrying chamber 61 is filled with fresh inactive gas.

[0073] After the replacement of the liquids is completed, the waferguide 62 moves up, as shown in FIG. 9 (S4 of FIG. 4). The wafers W arethen removed from the dichloromethane and introduced into the dryingchamber 61 while exposing them to the N₂ atmosphere. Dichloromethaneremaining on the wafer surface is vaporized and the wafers W are thusdried. It is preferable to discharge N₂ gas at normal temperature or hotN₂ gas onto the surface of each wafer W, as shown in FIG. 10 (S5 of FIG.4), thereby promoting the evaporation of dichloromethane and the dryingof the wafer. After drying, discharging of N₂ gas at normal temperatureor hot N₂ gas is stopped. Then, the cover 100 is opened, and a conveyerprovided at the loading/delivery section 50 transfers the wafers W outof the rinsing/drying unit 21.

[0074] By use of the above rinsing/drying unit 21, water contacting thesurface of each wafer W is replaced with dichloromethane without thewafers W coming into contact with air, and thereafter the wafers W, onwhich dichloromethane stays, are placed in the drying chamber 61. Thus,the wafers W can be dried without producing water marks, and formationof oxide film by natural oxidation due to the water marks can beprevented. This reduces defects of semiconductor devices, formed on thesurface of each wafer W.

[0075] Since dichloromethane does not dissolve a resist film, the wafersW with a resist film formed can be dried appropriately. As a result,breakage of the pattern can be prevented, and defects of semiconductordevices thus can be reduced.

[0076] Furthermore, since dichloromethane does not contain flammablecomponents such as alcohol and is fed into the processing bath 60 in aliquified state at normal temperature, there is little danger and thushigh-level safety measures and facilities are not required, compared tothe conventional process, in which wafers are dried using flammable IPAvapor.

[0077] Due to large heat of vaporization of dichloromethane, heat istaken from the wafers W at the time of vaporization, resulting inreduction in the surface temperature of the wafers W. It is thuspossible that steam (water vapor) in the atmosphere around the wafers Wis condensed and condensation is formed on the wafer surface. However,with the rinsing/drying unit 21, the drying chamber 61 (a space abovethe processing bath 60) is filled with an N₂ gas to prevent theatmosphere from containing steam, so that formation of condensation dueto evaporation of dichloromethane can be prevented.

[0078] Pure water, existing in the slots 108 and in the narrow regionsbetween the lower part of the periphery of each wafer W engaged with theslots 108 and the surface of each slot which are hardly dried ingeneral, is replaced with dichloromethane. Therefore, when the wafers Ware raised in the drying chamber 61, dichloromethane is vaporized andthus the lower part of the periphery of each wafer W can easily bedried. Furthermore, as compared with the conventional method in whichthe wafers W should be slowly raised from pure water into an IPAatmosphere in order to remove water by the Maragoni effect, theascending time of the wafers W can be shortened since just raising thewafers W out of dichloromethane is required.

[0079] Next, a rinsing/drying unit 110, which is the second embodimentof the present invention, will be explained. In the embodiment describedabove, the rinsing/drying unit 21 hot N₂ gas onto the wafers W in thedrying chamber 61. However, in the second embodiment, the rinsing/dryingunit 110 feeds hot N₂gas on to the wafers W in the processing bath 60.As shown in FIG. 11, the gas nozzles 94, 94 are arranged in pairs abovethe processing bath 60. The rinsing/drying unit 110 has the samestructure as that of the rinsing/drying unit 21 except for thearrangement of the gas nozzles 94, 94, accordingly, the same referencenumerals are assigned to the components having the same function andconstitution in FIGS. 2 and 11, and duplicate explanation will beomitted.

[0080] The process of the rinsing/drying unit 110 will be explainedreferring to the flow chart of FIG. 12 and FIGS. 13 to 15 illustratingprocessing steps 1 thru 3. In this process, as in the previouslydescribed process, dichloromethane is used as the solvent.

[0081] Firstly, the processing steps from the step of receiving wafersto the step of submerging the wafer in dichloromethane as shown in FIG.13 are executed in the same manner as the process using therinsing/drying unit 21. Next, hot N₂ gas is discharged from the gasnozzles 94, 94 so that the processing bath 60 is surrounded by an N₂atmosphere. Next, as shown in FIG. 14, dichloromethane is drained fromthe inner bath 63 (S4 shown in FIG. 12). As the liquid level lowers, thewafers W are exposed. Dichloromethane remaining on the surface of eachexposed wafer W is evaporated. As shown in FIG. 15, dichloromethane isalmost completely drained from the inner bath 63. Hot N₂ gas may be fedonto the wafers W in order to promote drying (S5 shown in FIG. 12).Thereafter, the wafer guide 62 moves up, and the wafers W are removedfrom the rinsing/drying unit 21.

[0082] Like the rinsing/drying unit 21, this rinsing/drying unit 110 canalso perform the drying process in safety without producing water marksand pattern breakage of a resist film deposited on the wafers W. Theperiphery of the lower part of each wafer W can be easily dried.

[0083] Next, a rinsing/drying unit 120, which is the third embodiment ofthe present invention, will be described. The above-mentionedrinsing/drying units 21 and 110 feed a solvent having a specific gravitygreater than that of pure water, while the rinsing/drying unit 120 feedsa solvent having a specific gravity smaller than that of pure water. Thesolvent has the same properties, as dichloromethane, except for thespecific gravity being smaller than that of pure water, namely, it isnonflammable and does not dissolve a resist film.

[0084] As shown in FIG. 16, a processing bath 121 has an inner bath 122and an outer bath 123. Solvent nozzles 124, 124 are arranged in pairs atthe upper portion of the processing bath 121. A solvent feed circuit 125is connected to the solvent nozzles 124, 124. A solvent feed source, notshown, is connected to an inlet of the solvent feed circuit 125. Anopen-close valve 126 and a flow rate controller 127 are sequentiallyprovided in the solvent feed circuit 125.

[0085] The process executed by the rinsing/drying unit 120 will bedescribed referring to illustrations FIGS. 17 to 20 showing theprocessing steps 1 thru 4, respectively. The flow of process isbasically the same as that executed by the rinsing/drying unit 21, andthus the flow chart of FIG. 4 will also be used for explanation.

[0086] Firstly, the processing steps from the step of receiving wafersto the step of submerging the water in pure water as shown in FIG. 17are executed in the same manner as the process carried out by therinsing/drying unit 21. After final rinsing, the open-close valve 126 isopened, and thus a solvent is fed into the inner bath 122, as shown inFIG. 18, by the solvent feed circuit 125 (S2 of FIG. 4). The solvent,the specific gravity of which is smaller than that of pure water, floatsabove the pure water occupying the upper part of the processing bath121. Relative to feeding of the solvent, pure water is gradually drainedfrom the inner bath 122 via a drain pipe 81 provided at the lower partof the processing bath 121. According to the above, a pure water layerand a solvent layer is formed in the inner bath 122. It is preferablethat the feed rate of solvent be equal to the drain rate of pure water.The solvent is accumulated and the solvent layer thus becomes thicker,while pure water is drained from the inner bath 122 and the pure waterlayer thus becomes thinner. As shown in FIG. 19, pure water stored inthe inner bath 122 is completely replaced with the solvent, and thewafers W are thus submerged in the solvent (S3 of FIG. 4). According tothe above, when the specific gravity of a solvent is smaller than thatof pure water, water contacting the wafer surface can also be replacedwith a solvent with the wafers W being kept submerged in the liquids(pure water and the solvent) and without the wafers contacting theatmosphere.

[0087] After the replacement, as shown in FIG. 20, the wafer guide 62moves up (S4 of FIG. 4), and then the solvent remained on the wafersurface is evaporated, and then N₂ gas at normal temperature or hot N₂gas is discharged onto the surface of each wafer W (S5 of FIG. 4).

[0088] By use of the above rinsing/drying unit 120, the same effects asthose obtained via usage of the rinsing/drying units 21 and 110 can beachieved.

[0089] In the rinsing/drying device 120, the wafers W can be covered bythe solvent without completely draining pure water from the processingbath 121. Namely, the process step shown in FIG. 19 can be replaced withthe process step shown in FIG. 21. As shown in FIG. 21, a solvent is fedinto the processing bath 121 and pure water is drained therefrom,thereby forming a solvent layer thick enough to entirely cover thewafers W and the wafer guide 62 therein. The wafer guide 62 then movesup and the wafers W are covered by the solvent layer. According to theabove, water contacting the surface of each wafer W can be replaced witha solvent without the wafers contacting with the atmosphere.

[0090] It is not necessary that the wafers W be kept still in thesolvent layer. Namely, the status of the wafers W can be changed from astate in which the wafers W contact with pure water to a state in whichthe wafers W contact with the solvent, upon forming the solvent layerand then moving the wafers W upward so that the wafers W pass throughthe solvent layer.

[0091] Next, a rinsing/drying unit 140, which is the fourth embodimentof the present invention, will be described. The rinsing/drying unit 140is configured onto feed a solvent having a specific gravity smaller thanthat of pure water and feed N₂ gas at normal temperature or hot N₂ gasonto the wafers W into the processing bath 121. As shown in FIG. 22, thegas nozzles 94, 94 are arranged in pairs above the processing bath 121.

[0092] The process executed by the rinsing/drying unit 140 is basicallythe same as that executed by the rinsing/drying unit 110 explained uponreferring to FIGS. 13 to 15.

[0093] Namely, firstly, the wafers W are submerged in the solvent, thesolvent is drained from the inner bath 122, and then N₂ gas at normaltemperature or hot N₂ gas is fed onto the wafers W in the processingbath 121. By use of the rinsing/drying unit 140, the same effect asthose of the rinsing/drying units 21, 110 and 140 mentioned above can beobtained.

[0094] It should be noted that the present invention is not limited tothe aforementioned embodiments and other various embodiments arepossible. For example, the above-mentioned rinsing/drying units 21 and110 feed dichloromethane (i.e., a solvent greater than pure water inspecific gravity) from the lower part of the processing bath 60,however, such a solvent may be fed from the upper part of the processingbath 60. Furthermore, the rinsing/drying units 120 and 140 feed asolvent having a smaller specific gravity than that of pure water fromthe upper part of the processing bath 121, however, such a solvent maybe fed from the lower part of the processing bath 121. Furthermore, therinsing/drying units 21, 110, 120 and 140 may be may be structured as aunit of a so-called “one-bath” type, which can execute not only rinsingby pure water but also cleaning using a chemical liquid such as afluoride acid. In this case, chemical liquid cleaning and pure waterrinsing can be executed continuously in the processing bath 60, therebysaving foot print and improving throughput.

[0095] The present invention is applicable not only to a batch processthat processes a plurality of substrates in a batch but also to asingle-wafer type process that processes substrates one by one. Thesubstrate may be an LCD substrate, a CD substrate, a printed substrateor a ceramic substrate, as well as a semiconductor wafer as exemplifiedabove.

[0096] HFE (hydrofluoroether) which has a specific gravity greater thanthat of pure water, is hydrophobic, does not dissolve a resist film, isanother example of the solvent liquid that can be used in the first andsecond embodiments. HFE-7100, provided by Sumitomo 3M Kabushiki Kaisha,is known as a commercially available HFE. When HFE is fed into the innerbath in the same manner as that of feeding HMDS or dichloromethane, thecondition of the interface between HFE, pure water, and a wafer becomesas shown in FIG. 23. Namely, pure water lighter than HFE is positionedabove HFE, and pure water enters into the HFE side in the neighborhoodof an interface between the wafer and the liquids (HFE and pure water).

[0097] Under such conditions, even if the interface between the HFE andpure water is raised by further feeding HFE into the inner bath, it ispossible that minute amounts of pure water remain on the wafer W, thatis, minute amounts of pure water adhering to the wafer W are pulled inunder the interface between the pure water and the HFE, and remains onthe surface of the wafer W without being replaced with HFE.

[0098] The remaining pure water might produce water marks after raisingthe wafer from the HFE and before drying the wafer. To solve thisproblem, the interfaces between HFE, pure water and wafer W may be setas shown in FIG. 24 so that pure water is hardly pulled into the HFEside.

[0099] As shown in FIG. 25, an IPA feed circuit 170 for feeding minuteamounts of IPA (isopropyl alcohol) separately from HFE is available asone means for obtaining the interface condition as shown in FIG. 24. TheIPA feed circuit 170 is composed of an IPA feed source connected to thesolvent feed circuit 70, an open-close valve 171, and a flow ratecontroller 172.

[0100] When HFE mixed with a small amount of IPA is fed to the innerbath by the IPA feed circuit 170, a thin IPA film is formed between thepure water and the HFE. Then, the contact angle of the interface withthe wafer is changed, and HFE enters into the pure-water side in theneighborhood of the interface between the wafer and the liquids (HFE andpure water).

[0101] In other words, the interface between the pure water and the HFEis inclined toward the upper side (i.e., toward the direction in whichthe interface between pure water and HFE moves during replacement ofpure water with HFE in the inner bath,) as shown in FIG. 24. Therefore,when HFE is continuously fed so as to move the interface between thepure water and the HFE, the pure water is completely replaced with HFEwith no pure water remaining on the wafer.

[0102] As shown in FIG. 26, a solvent heating means for heating HFE maybe used as alternative means for obtaining the above-mentioned effect.The solvent heating means comprises, for example, a heater 173 attachedto the solvent feed circuit 70. HFE is heated by the solvent heatingmeans and fed to the inner bath 63. Since the contact angle of theheated HFE and the wafer is changed, HFE enters into pure-water side inthe neighborhood of the interface between the wafer and the liquids (HFEand pure water), as shown in FIG. 24. Therefore, when heated HFE iscontinuously fed so as to move the interface between pure water and HFE,pure water is completely replaced with HFE with no pure water remainingon the wafer.

What is claimed is:
 1. A substrate processing method comprising thesteps of: placing a substrate in a first processing liquid stored in aprocessing bath; feeding a second processing liquid different inspecific gravity from the first processing liquid into the processingbath, thereby forming a first layer of the first processing liquid and asecond layer of the second processing liquid with an interface beingformed therebetween; and causing a relative movement of the interfaceand the substrate so that the substrate passes through the interface andthe substrate locates at a second layer side of the interface.
 2. Thesubstrate processing method according to claim 1, wherein the secondprocessing liquid is substantially insoluble in the first processingliquid.
 3. The substrate processing method according to claim 1, whereinthe relative movement of the interface and the substrate is produced bydraining the first liquid from the processing bath while feeding thesecond processing liquid into the processing bath.
 4. The substrateprocessing method according to claim 1, wherein the specific gravity ofthe second processing liquid is smaller than that of the firstprocessing liquid, and the relative movement of the interface and thesubstrate is produced by draining the first liquid from a lower part ofthe processing bath, while feeding the second processing liquid into theprocessing bath.
 5. The substrate processing method according to claim4, wherein the second processing liquid is fed from an upper part of theprocessing bath.
 6. The substrate processing method according to claim5, wherein a feed rate the second processing liquid is equal to adischarge rate of the first processing liquid.
 7. The substrateprocessing method according to claim 4, further comprising the steps of:positioning the substrate above the processing bath after the substratehas contacted the second processing liquid; and supplying a gas to thesubstrate above the processing bath to dry the substrate.
 8. A substrateprocessing method according to claim 4, further comprising the steps of:draining the second processing liquid from the lower part of theprocessing bath after the first processing liquid has completely beendrained from the processing bath, thereby positioning the substrateoutside the second processing liquid with the substrate being positionedin the processing bath; and feeding a gas to the substrate positioned inthe processing bath to dry the substrate.
 9. The substrate processingmethod according to claim 1, wherein the specific gravity of the secondprocessing liquid is greater than that of the first processing liquid,and the relative movement of the interface and the substrate is producedby overflowing the first processing liquid from an upper part of theprocessing bath to drain the first processing liquid from the processingbath, while feeding the second processing liquid into the processingbath.
 10. The substrate processing method according to claim 9, whereinthe second processing liquid is fed from a lower part of the processingbath.
 11. The substrate processing method according to claim 9, furthercomprising the steps of: positioning the substrate above the processingbath after the first processing liquid has been drained from theprocessing bath by overflowing the first processing liquid from theupper part of the processing bath; and feeding a gas to the substrateabove the processing bath to dry the substrate.
 12. The substrateprocessing method according to claim 9, further comprising the steps of:draining the second processing liquid from a lower part of theprocessing bath after the first processing bath has completely beendrained from the processing bath by overflowing the first processingliquid from the upper part of the processing bath, thereby positioningthe substrate outside the second processing liquid with the substratebeing positioned in the processing bath; and feeding a gas to thesubstrate positioned in the processing bath to dry the substrate. 13.The substrate processing method according to claim 1, wherein thespecific gravity of the second processing liquid is smaller than that ofthe first processing liquid, and the relative movement of the interfaceand the substrate is produced by moving the substrate upward.
 14. Thesubstrate processing method according to claim 1, further comprising thestep of positioning the substrate outside the second layer and dryingthe substrate, after the completion of the step of causing the relativemovement of the interface and the substrate to pass the substratethrough the interface.
 15. The substrate processing method according toclaim 14, wherein in the step of drying the substrate, an inert gasatmosphere is established around the substrate.
 16. The substrateprocessing method according to claim 1, wherein a resist film is formedon a surface of the substrate and the second processing liquid has aproperty of not-dissolving the resist film.
 17. The substrate processingmethod according to claim 1, wherein the second processing liquid isnon-flammable.
 18. The substrate processing method according to claim 1,wherein, when the second processing liquid is fed, a third processingliquid is fed, the third processing liquid being substantially insolublein the first and the second processing liquids and having a specificgravity between those of the first and the second processing liquids isfed, thereby a third layer of the third processing liquid is formedalong the interface between the first layer and the second layer,whereby the interface inclines so that, the interface, according to itsproximity of the substrate, dislocates in a moving direction of theinterface relative to the substrate when the relative movement iscarried out.
 19. The substrate processing method according to claim 1,wherein the second processing liquid is fed to the processing bath in aheated state, whereby the interface inclines so that, the interface,according to its proximity of the substrate, dislocates in a movingdirection of the interface relative to the substrate when the relativemovement is carried out.